1. Field of the Invention
The present invention relates to a coil device preferably used for a resonance transformer and the like.
2. Description of the Related Art
Coil devices are used in various electrical products for various uses. For instance, when driving a backlight of liquid crystal display, an inverter resonance transformer is used to obtain a high-voltage.
A resonance transformer is requested to realize outward requirements such as low height profile, in addition to electric characteristics such as occurrence of suitable leakage inductance. In order to meet such requirements, prior art proposes a coil device which is a horizontal-type wherein the axis direction of core is parallel to the mounting surface, and which is a split structure wherein a primary coil and a secondary coil are separately arranged along the axis direction of core. Further, there is advantage that the coil device of the split structure is relatively easy to insulate.
However, the coil device according to prior arts has problems that a leakage flux occurs toward a downward direction of a mounting surface of the coil device or toward an upward direction. For instance, as for a resonance transformer used for a backlight of liquid crystal display television, constructional materials including iron and the like may be disposed upward and downward directions of the coil device. With this, it brings problems that a leakage flux from the coil device causes eddy current in constructional material and the like, and then heat or noise associated with said occurrence of eddy current are caused. Further, in order to prevent such leakage flux toward upward and downward directions, it is possible to implement an aluminum board on upward and downward directions of the coil device. However, with this implement, heat dissipation of a coil may be deteriorated.
In order to resolve the above problems, the applicant has proposed a coil device to realize low height profile of a coil device, by combining a bobbin plate to which a primary coil winds and a case to which a secondary coil winds, and then disposing the secondary coil at the outer circumference of the primary coil.
However, in regard with the coil device under development, it is necessary to pull and connect a lead part of the secondary coil which is wound around a case to a secondary terminal which is formed at an end portion of the bobbin plate. Currently, there is a problem that it is difficult to automate that operation.
[Patent Document 1] Japanese Patent Publication No. 2008-112753.